Bed frames having end rails of adjustable length to the end that the frame is of adjustable width to accommodate different sizes of bedding are well known in the art. In such bed frame constructions each of the end rails consists of two rail members which are in nested, telescoped relationship and which are so structured as to enable them to be locked together in any of a number of telescoped positions so as to provide the desired end rail length, and hence bed frame width. The features sought in any such bed frame end rail structure are: minimum number of detachable components to the end that there is minimum possibility of an essential component becoming lost or misplaced; ample end rail strength to carry all expected loading on the end rails; optimum simplicity of adjustment, with the manner of making the adjustment being manifest from the adjustment structure itself without need for any instructions as to its operation; optimum assurance against any accidental unlocking of the end rail members from their locked, adjusted position; and optimum simplicity of construction and low manufacturing costs, commensurate with accomplishing these features.
As regards the rail members which form the end rail, they can be of box construction, of C-cross section channel construction, or they can be angle irons, i.e. of L-shaped cross section. In terms of cost, the latter are generally preferred. However, the use of angle irons puts a premium on requirement for an adjustment and adjustment lock construction providing maximum assurance that the nested, telescoped portions of the rail members remain firmly locked in their nested, mutually reinforcing relationship once the bed frame is assembled to the desired width. Unnesting of the rail members, with resultant frame failure, can occur simply by way of the members unauthorizedly becoming disconnected or by way of the members becoming bent or twisted under load. To best assure against the latter it is desirable that there be a mimimum number of openings through the rail members since large numbers of openings weaken the rail members.
U.S. Pat. No. 3,871,039 shows an adjustable bed frame having the various features mentioned above, save only that it is of relatively high-cost construction by reason of the channel-shaped rail members it incorporates.
U.S. Pat. No. 3,795,022 shows an adjustable bed frame incorporating angle iron rail members; however, the adjustment and locking means involves the use of a relatively large number of openings, openings in both the vertical and horizontal flanges of one rail member and an opening in the horizontal flange of the other rail member--and at that with the openings in the two rail members being aligned thereby further imparting weakness to the nested rails.